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57 results for “Amazonian River”
Fig. 8 in Systematics and biogeography of Sternarchellini (Gymnotiformes: Apteronotidae): Diversification of electric fishes in large Amazonian rivers
Fig. 8. PCA scatter plot of species in the S. terminalis species group. Loadings of all 13 variables for PC2 reported in lower panel. Sternarchella terminalis represented as squares (n= 45), S. orthos as circles (n= 54), and Sternarchella sp. A represented as an X (n= 1).
Data from: Testing main Amazonian rivers as barriers across time and space within widespread taxa
Aim: Present Amazonian diversity patterns can result from many different mechanisms and, consequently, the factors contributing to divergence across regions and/or taxa may differ. Nevertheless, the river-barrier hypothesis (RBH) is still widely invoked as a causal process in divergence of Amazonian species. Here we use model-based phylogeographic analyses to test the extent to which major Amazonian rivers act similarly as barriers across time and space in two broadly distributed Amazonian taxa. Local: Amazon rainforest. Taxon: The lizard Gonatodes humeralis (Sphaerodactylidae) and the tree frog Dendropsophus leucophyllatus (Hylidae). Methods: We obtained RADseq data for samples distributed across main river barriers, representing main Areas of Endemism previously proposed for the region. We conduct model-based phylogeographic and genetic differentiation analyses across each population pair. Results: Measures of genetic differentiation (based on FST calculated from genomic data) show that all rivers are associated with significant genetic differentiation. Parameters estimated under investigated divergence models showed that divergence times for populations separated by each of the 11 bordering rivers were all fairly recent. The degree of differentiation consistently varied between taxa and among rivers, which is not an artifact of any corresponding difference in the genetic diversities of the respective taxa, or to amounts of migration based on analyses of the site-frequency-spectrum. Main conclusions: Taken together, our results support a dispersal (rather than vicariance) history, without strong evidence of congruence between these species and rivers. However, once a species crossed a river, populations separated by each and every river have remained isolated – in this sense, rivers act similarly as barriers to any further gene flow. This result suggests differing degrees of persistence and gives rise to the seeming contradiction that the divergence process indeed varies across time, space, and species, even though major Amazonian rivers have acted as secondary barriers to gene flow in the focal taxa.
Data from: Amazonian rivers are leaky barriers to gene flow in forest understory birds
<p>Ever since Alfred Russel Wallace's nineteenth-century observation that related terrestrial species are often separated on opposing riverbanks, major Amazonian rivers have been recognized as key drivers of speciation. However, rivers are dynamic entities whose widths and courses may vary through time. It thus remains unknown how effective rivers are at reducing gene flow and promoting speciation over long timescales. We fit demographic models to genomic sequence to reconstruct the history of gene flow in three pairs of avian taxa fully separated by different Amazonian rivers, and whose geographic ranges do not make contact in headwater regions. Models with gene flow were best fit, but still supported an initial period without any gene flow which ranged from 187,000 to over 959,000 years, suggesting that rivers are capable of initiating speciation through long stretches of allopatric divergence. Allopatry was followed by either bursts or prolonged episodes of gene flow that retarded genomic differentiation but did not homogenize populations. Our results support Amazonian rivers as key barriers that promoted speciation and the buildup of species richness, but they also suggest that river barriers are often leaky, with genomic divergence accumulating slowly due to episodes of substantial gene flow.</p>
Fig. 5 in A new glassfrog (Centrolenidae: Hyalinobatrachium) from the Topo River Basin, Amazonian slopes of the Andes of Ecuador
Fig. 5. Distribution of Hyalinobatrachium adespinosai sp. nov. in Ecuador.
Fig. 2 in A new glassfrog (Centrolenidae: Hyalinobatrachium) from the Topo River Basin, Amazonian slopes of the Andes of Ecuador
Fig. 2. Hyalinobatrachium adespinosai sp. nov. in life, holotype.
Functional responses of fisheries to hydropower dams in the Amazonian Floodplain of the Madeira River
<p>1. Tropical river fisheries support food security for millions of people but are increasingly threatened by hydropower development. How dams affect these fisheries remains poorly known in most regions. Here, we used a functional traits approach to evaluate the extent to which the composition of fishery yields in the Madeira River Basin the largest sub-basin in the Amazon, respond to dam construction. We also explored how dams affected the monetary value of yields and fishing-based income of the communities.</p> <p>2. We collected fishing data in 17 locations distributed more than 300 km across upstream, reservoir, and downstream zones during pre-and post-dam construction periods. We interviewed 711 fishers from 13 communities to assess fishing income during pre- and post-dam periods.</p> <p>3. Catch-per-unit effort (CPUE) declined significantly, i.e., by 37%, after dam construction. Multivariate analysis yielded six species clusters according to trait syndromes related to life history, migration, swimming-performance/microhabitat-use and economic value that were associated with the environmental data characteristic of pre- and post-dam periods. Comparison of CPUE of each cluster indicated that large species with periodic life-history strategy and regional or long-distance migratory behavior were most affected by dam construction, with CPUE declining by, on average, 31%. Declines in yields and shifts in functional composition of the fishery yields resulted in average decline of 21% in the monetary of functional clusters and 30% in fishing income.</p> <p>4. Synthesis and applications. Our study indicates that the implementation of the dams and associated changes in environmental conditions affected the functional composition of yields and reduced catches, negatively affecting the fishing-based income of the studied communities in the Madeira River.Whereas catches of all functional clusters declined after the dams, species possessing large body sizes, traits related to a periodic life history strategy, either with long-distance or regional migratory behaviors, and the greatest economic importance appeared to be particularly vulnerable. These results imply that hydropower expansion will cause detrimental effects for fisheries and the livelihoods they sustain. Our results underscore the urgent need for considering alternative sources of renewable energy (e.g., solar power and in-stream turbines) to avoid irreversible socio-environmental damages of large dam projects. In river reaches where dams are already in operation or under construction, minimizing impacts will require improving operational protocols to reduce hydrological alterations and developing research and technology to improve the functionality of fish passages. In these locations, addressing losses in fishery value and fishing-based income will also require the implementation of fair compensation measures. Maintaining fish production requires conserving flow pulses and free-flowing rivers and tributaries critical for completing life cycles of fish species with vulnerable traits.</p>
Functional responses of fisheries to hydropower dams in the Amazonian Floodplain of the Madeira River
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Data from: Testing main Amazonian rivers as barriers across time and space within widespread taxa
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Data from: Habitat amount hypothesis and passive sampling explain mammal species composition in Amazonian river islands
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Data from: Amazonian rivers are leaky barriers to gene flow in forest understory birds
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Data from: Arboreal ant abundance tracks primary productivity in an Amazonian whitewater river system
Little is known about consumer productivity in the tropics despite the key feedbacks that animals impose on primary productivity. In the Amazon basin, seasonally flooded and unflooded forests exist side by side, and ants (Formicidae) dominate animal biomass. Although flooding has a direct, negative effect on soil-dwelling ants, it is less clear whether flooding has indirect effects on arboreal ants via associated changes in tree communities. To test whether seasonal inundation by whitewater affects arboreal ants, we investigated ant communities in adjacent flooded and unflooded forests along a major whitewater river in central-western Amazonia. Whitewater-flooded forest exhibits higher primary productivity than unflooded forest. We thus hypothesized that forest type would affect the productivity and the foraging traits of arboreal ants, and that these changes would be mediated by increases in plant-derived food for ants in flooded forest. We compared ant and plant communities between flooded and unflooded forest transects along the Juruá River in Amazonas, Brazil. We collected, identified, and counted terrestrial and arboreal ants, and we measured ant traits with putative relationships to foraging strategy. We also identified plant stems to characterize the abundance of ant food rewards. Flooding negatively affected the diversity and abundance of terrestrial ants but did not change the diversity of arboreal ants. Arboreal ants were more abundant and exhibited higher biomass in flooded forest than in unflooded forest. Arboreal ant traits also suggested that ants may rely more heavily on plant-derived food in flooded forest than in unflooded forest. These differences were associated with a higher abundance of plant stems predicted to contain ant food rewards in flooded forest than in unflooded forest. Our results indicate that the productivity of arboreal ants is affected by that of the underlying forest. Such effects may be mediated by the predominantly herbivorous foraging strategy of canopy ants, which would link ant populations closely to primary production and stoichiometry. Given ants' important functional roles, these differences in ant productivity between forest types may have consequences for other arthropods and feedbacks to plants throughout the Amazon basin.
Data from: Bird assemblages on Amazonian river islands: patterns of species diversity and composition
The principles of island biogeography are rarely used to investigate the animal assemblages of Amazonian river islands. Here, we apply this approach to compare bird assemblages of Amazonian river islands with a variety of mainland habitats. We also examine how bird species diversity and composition are related to island physical attributes. Birds were sampled with mist nets and qualitative censuses on 11 river islands and at 24 mainland sites on the lower reaches of the Rio Negro in the Brazilian Amazon. Island bird assemblages are characterized by lower species richness and a higher abundance of a few dominant species. Additionally, species composition of the islands was significantly distinct from the mainland, including the nearby floodplain habitats. Number of bird species increased with island size and habitat diversity, and decreased with degree of isolation. In addition, small islands tended to harbour an impoverished subset of the species present on larger ones. Bird species diversity and composition on Amazonian river islands are likely influenced by the ecological succession and historical events affecting island formation. Considering their small total area across the Amazon basin, these insular fluvial environments could be disproportionally threatened by river channel disturbances such as climate change events, and hydroelectric building.
Subspecies and Distribution. C. p. pygmaea Spix, 1823 — Upper Amazon in S Colombia, W Brazil, E Ecuador, and N Peru, N of the Amazon River and left bank of the Rio Pastaza, E to the mouth of the Rio Japura, and S of the Rio Japura-Caqueta to the Andes. C. p. niverventris Lonnberg, 1940 — Amazonian lowlands and Andean foothills in W Brazil, E Peru, and N Bolivia, S of the Amazon River, E of the Rio Mayo and the Rio Huallaga above the Rio Mayo, S to the upper Rio Purus, E to N Bolivia (Rio Muyumanu), and N probably through the entire interfluvium of the rios Purus and Madeira. in Callitrichiade
Subspecies and Distribution. C. p. pygmaea Spix, 1823 — Upper Amazon in S Colombia, W Brazil, E Ecuador, and N Peru, N of the Amazon River and left bank of the Rio Pastaza, E to the mouth of the Rio Japura, and S of the Rio Japura-Caqueta to the Andes. C. p. niverventris Lonnberg, 1940 — Amazonian lowlands and Andean foothills in W Brazil, E Peru, and N Bolivia, S of the Amazon River, E of the Rio Mayo and the Rio Huallaga above the Rio Mayo, S to the upper Rio Purus, E to N Bolivia (Rio Muyumanu), and N probably through the entire interfluvium of the rios Purus and Madeira.
Distribution. NE Amazonian lowlands N of the Amazon River and E of Orinoco and Rio Negro rivers in E Venezuela, the Guianas, and N Brazil. in Erethizontidae
Distribution. NE Amazonian lowlands N of the Amazon River and E of Orinoco and Rio Negro rivers in E Venezuela, the Guianas, and N Brazil.
Distribution. Amazonian Brazil, in Amazonas and Para states E of the Rio Madeira and along the S bank of the Amazon River, including at least part of Marajo I. Distribution may extend into adjacent Atlantic coastal watershed of Maranhao State. in Erethizontidae
Distribution. Amazonian Brazil, in Amazonas and Para states E of the Rio Madeira and along the S bank of the Amazon River, including at least part of Marajo I. Distribution may extend into adjacent Atlantic coastal watershed of Maranhao State.
Distribution. Amazonian lowlands of E Brazil S of the Amazon River, extending S to the cerrado biome in EC Brazil, primarily in the Rio Tapajos, Rio Xingu, and Rio Tocantins-Araguaia fluvial systems of Para, Maranhao, Tocantins, Minas Gerais, Goias, and Mato Grosso states. in Echimyidae
Distribution. Amazonian lowlands of E Brazil S of the Amazon River, extending S to the cerrado biome in EC Brazil, primarily in the Rio Tapajos, Rio Xingu, and Rio Tocantins-Araguaia fluvial systems of Para, Maranhao, Tocantins, Minas Gerais, Goias, and Mato Grosso states.
Distribution. Amazonian Brazil (Amazonas State), S of the Rio Solimoes, E of the lower Rio Jurua, and W of the Purus/Tapaua river system; the S limit ofits geographic distribution remains unclear. in Phitheciidae
Distribution. Amazonian Brazil (Amazonas State), S of the Rio Solimoes, E of the lower Rio Jurua, and W of the Purus/Tapaua river system; the S limit ofits geographic distribution remains unclear.
Distribution. NE & S Venezuela (Orinoco Delta and S of the Orinoco River), the Guianas, N & NC Brazil (along the Amazon River W to Maranhao and S to Para and Mato Grosso states), and into upper Amazon Basin of SW Colombia (N up to Meta and Guainia departments), E Ecuador, and NE & E Peru; its S limit in W Amazonian Brazil is unclear. Additional visual records are described for SE Para State and need to be confirmed. in Megalonychidae
Distribution. NE & S Venezuela (Orinoco Delta and S of the Orinoco River), the Guianas, N & NC Brazil (along the Amazon River W to Maranhao and S to Para and Mato Grosso states), and into upper Amazon Basin of SW Colombia (N up to Meta and Guainia departments), E Ecuador, and NE & E Peru; its S limit in W Amazonian Brazil is unclear. Additional visual records are described for SE Para State and need to be confirmed.
Data from: The interplay of dispersal limitation, rivers, and historical events shapes the genetic structure of an Amazonian frog
Disentangling the impact of landscape features such as rivers and historical events on dispersal is a challenging but necessary task to gain a comprehensive picture of the evolution of diverse biota such as that found in Amazonia. Adenomera andreae, a small, territorial, terrestrial frog species of the Amazonian forest represents a good model for such studies. We combined Cytochrome b sequences with 12 microsatellites to investigate the genetic structure at two contrasted spatial scales in French Guiana: along a ~6 km transect to evaluate dispersal ability and between paired bank populations along a ~65 km stretch of the Approuague river to test the effect of rivers as barriers to dispersal. We observed significant spatial genetic structure between individuals at a remarkably small geographical scale and conclude that the species has a restricted dispersal ability likely tied to its life history traits. Mitochondrial and microsatellite data also indicate a high level of differentiation among populations on opposite banks of the river and, in some cases, among populations on the same riverbank. These results suggest that the observed population structure in A. andreae is due to restricted dispersal abilities combined with the action of rivers and Quaternary population isolation. Given that Amazonia hosts a great portion of anurans, as well as other small vertebrates, that display life history traits comparable to Adenomera andreae, we argue that our analyses provide new insights into the complex interactions among evolutionary processes shaping Amazonian biodiversity.
Data from: The interplay of dispersal limitation, rivers, and historical events shapes the genetic structure of an Amazonian frog
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